Many subterranean formations contain hydrocarbon based fluids, e.g. oil or gas, that can be produced to a surface location for collection. Generally, a wellbore is drilled, and a completion is moved downhole to facilitate production of desired fluids from the surrounding formation. In many applications, the wellbore completion includes one or more well tools, such as packers, valves or other tools useful in a given application, that are selectively actuated once the completion is deployed in the wellbore.
Actuation of many well devices is accomplished by physically moving a mechanical actuating member that changes the tool from one state to another. Examples include moving a valve from a closed position to an open position, setting a packer, or actuating a wide variety of other well tool types. The force to actuate such well tools can be provided by, for example, hydraulic pressure, solenoid actuators or combinations of electric motors, gear boxes and ball screw actuators.
Actuation of a well device typically occurs during movement of the completion downhole or after the completion has been fully deployed at the downhole location. Often, the downhole environment in which such tools are operated is a relatively harsh environment, susceptible to relatively high temperatures, pressures and deleterious substances. Accordingly, actuators having a high degree of complexity in construction or operation can have an increased susceptibility to malfunction due to the adverse conditions.